docs: def month_boundaries(dt=None):
      '''
      Return a 2-tuple containing the datetime instances for the first and last
      dates of the current month or using ``dt`` as a reference.
  
      '''
      dt = dt or date.today()
      wkday, ndays = calendar.monthrange(dt.year, dt.month)
      start = datetime(dt.year, dt.month, 1)
      return (start, start + timedelta(ndays - 1))